I hope your relationship continues to improve. Based on everything that you've said here, you've been a saint to stay with your spouse! I hope you're able to stay strong while she gets better; it sounds like you want to save your marriage and after 15 years if commitment I can understand why. I cheated on my spouse too. She discovered what I was doing and confronted me about it (and I confessed), but it took a long time and a lot of sacrificing on both our parts to fix what I broke. But your situation sounds more taxing - you have to contend with her bipolar situation and her dishonesty (which can often accompany bipolar disorders). I have a lot of respect for what you're doing and wish you all the best.
Take the risk of thinking for yourself, much more happiness, truth, beauty, and wisdom will come to you that way. - C. Hitchens
Me: Male, bi, 48, flexible